Constraints on Axion-like Particles from the Observation of GRB 221009A by LHAASO

Abstract

Recently, the LHAASO collaboration reported the measurement of the gamma-ray spectra of GRB 221009A, which is the brightest burst ever, covering an energy range from 0.3 to about 10 TeV. Based on the observation by LHAASO, we examine the ALP-photon oscillation effect in the host galaxy of GRB 221009A and Milky Way. Considering the uncertain magnetic field configuration in the host galaxy, we set constraints on the ALP parameters with three different models: a homogeneous magnetic field model, a model same as the Galactic magnetic field model, and a model constructed from the HST observations of the host halo. The \({\rm CL_s}\) method is applied to set the constraints in this study. We find that the constraints derived with three host galaxy magnetic field models are comparable. Our results are complementary in the small ALP mass regions compared with other experiments.